Thanks Semper.
It was a friend that pointed this out (a few years ago) and I keep the containers in the spare bathtub

(This bathroom also has a separate shower
so the tub is Very Rarely used!).
I had not thought of this til the friend said something and I felt "dumb as a box of rocks" that I had Not thought of it.
You are right Semper - I think it is a case of the "Forest for the Trees" type thinking.